Mass spectrometry imaging developments

New Developments in Mass Spectrometry 2.11.1 Mass Spectrometry Imaging... 

MALDI-IMS is still limited to about 20 pm spatial resolution (with 10-50 pm the most commonly achievable spatial resolution at this time), typically obtained with commercial ion sources (80). Recently, Zavalin et al. demonstrated that 5 pm spatial resolution can be achieved for MALDI-IMS instruments by spatial filtration of the laser beam by using a 25 pm ceramic pinhole filter (81). Secondary ion mass spectrometry (SIMS), developed in the 1960s (82), offers a complementary or alternative method to MALDI-IMS and other matrix-free LDI-MS methods for the acquisition of higher spatial resolution images. In SIMS, a focused high-energy primary ion beam (such as Cs+, Au3+, Bi5+, or C60+) is used to directly bombard the sample... 

Nevertheless, the introduction of time-of-flight (ToF) analysers for SIMS analyses at the beginning of the 1980s, as well as the recent development of liquid ion sources delivering cluster projectiles now permit the analysis of organic materials with high sensitivity and selectivity. Moreover, thanks to its excellent lateral resolution (in the order of micrometres), and its minimal sample preparation, ToF-SIMS has become the reference technique for chemical imaging by mass spectrometry. 

The development of surface analytical techniques such as LA-ICP-MS, GDMS and SIMS focuses on improvements to sensitivity and detection limits in order to obtain precise and accurate analytical data. With respect to surface analytical investigations, an improvement of spatial and depth resolution is required, e.g., by the establishment of a near field effect or the apphcation of fs lasers in LA-ICP-MS. There is a need for the improvement of analytical techniques in the (j,m and nm range, in depth profiling analysis and especially in imaging mass spectrometry techniques to perform surface analyses faster and provide more accurate data on different materials to produce quantitative 3D elemental, isotopic and molecular distribution patterns of increased areas of interest with high spatial and depth resolution over an acceptable analysis time. 

Use of Matrix Assisted Laser Desorption/ Ionization Imaging Mass Spectrometry (MALDI-IMS) in the Development of Novel Small Molecule Drugs... 

Chaurand P, Rahman M, Hunt T, Mobley J, Gu G, Latham J, Caprioli R, Kasper S (2008) Monitoring mouse prostate development by profiling and imaging mass spectrometry. Mol Cell Proteomics 7 411-423. doi 10.1074/mcp.M700190-MCP200... 

Chaurand P, Norris J, Cornett D, Mobley J, Caprioli R (2006) New developments in profiling and imaging of protein from tissue sections by MALDI mass spectrometry. J Proteome Res 5 2889-2900. doi 10.1021/pr060346u... 

Ifa D, Wiseman J, Song Q, Cooks G (2007) Development of capabilities for imaging mass spectrometry under ambient conditions with desorption electrospray ionization (DESI). Int J Mass Spectrom 259 8-15. doi 10.106/j.ijms.2006.08.003... 

The results obtained with this first generation focal plane M.S.-EOID system as well as studies by Beynon and others at Purdue University (15) demonstrated the technical feasibility of such a system. Furthermore, these studies led the way to solutions for the variety of fundamental problems, which were encountered during the development and helped point out the directions towards future changes necessary on the road towards a commercially practical design for use of the concept in routine applications of mass-spectrometry. It became obvious that the vidicon based camera system wets not the best approach. Some of the reasons for this are (1) Loss of sensitivity due to light losses in the dissector and the transfer optics (2) cost of the image dissector (3) lower dynamic range and sensitivity, slower read-out rate, etc., of the vidicon compared to alternate devices. 

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